Most 3D display techniques developed to date are stereoscopic. A stereoscopic system may be realized that may display large images with high resolution, however stereoscopic techniques may require supplementary glasses to evoke 3-D visual effects. Additionally, stereoscopic techniques may provide observers with horizontal parallax and a small number of viewpoints. Observation of stereoscopic images may also cause visual fatigue due to convergence-accommodation conflict.
Convergence-accommodation conflict may be avoided by a true 3-D image formation in space with full parallax and continuous viewing points. Holography is one way to form 3-D images in space, but recording full-color holograms for an outdoor scene may be difficult. For example, when computer-generated holograms are prepared, a large amount of computation time and capacity may be required to obtain proper gratings. Because coherent light is often used in holography, speckle may also occur.
To produce true 3-D images in space with incoherent light using two-dimensional (2-D) display devices, techniques based on ray optics have also been studied. One technique may be referred to as integral imaging (II).
In II, 3-D images may be formed by crossing the rays coming from 2-D elemental images using a lenslet array. Each microlens in a lenslet array may act as a directional pixel in a pinhole fashion. The pinholes create directional views which when viewed with two eyes for example, appear as a 3D image in space. II may provide observers with true 3-D images with full parallax and continuous viewing points. However, the viewing angle, depth-of-focus, and resolution of 3-D images may be limited.
In addition, 3-D images produced in direct camera pickup II are pseudoscopic (depth-reversed) images, and thus may make II systems more complex and thus more impractical.
Advancements in the art are needed to increase viewing angles and improve image quality. Also needed are ways to display, images of large objects that are far from the pickup device. Additionally needed advancements include the ability to project 3-D images to a large display screen.